German patent document DE 102 10 130 A1 discusses a method and a device for warning a driver, in which a degree of driver attention or driver inattention is taken into consideration. This degree of attention, i.e. the state of the driver, is derived from the steering angle, especially from the change in the steering angle, for instance, of the gradient and/or the frequency of the angle changes and/or the spacing of successive steering angle changes. In addition, further influence variables for detecting the driver state are described, such as the gas pedal position and its change.
German patent document DE 102 38 324 A1 discusses a procedure for driver state detection, in which steering angle data and data of a track detection are taken into consideration. A decreased driver attention is discussed, with the aid of the monitoring of the steering wheel angle compared to a specified limiting angle, by monitoring the rotary speed at which the driver turns the steering wheel, and the monitoring of the distance of the vehicle from the lane sidelines compared to a specified limiting value. Furthermore, the frequency and the duration of states of rest of the driver, in which he undertakes no steering intervention, is also taken into consideration.